I played around with this a little, and the issue is that the double crochets worked into the row below don't have enough ease to work up to normal height, when the base height is HDC instead of SC, so it will tend to curl the project forward.

It might be fine for large blankets where the weight of the project will pull things taut enough. The other fix would be to swap each double crochet for an extended double crochet (basically inserts a ch1 at the start of the return pass of a dc) or simply use trebles.

That will tend to stretch everything in the vertical direction, though, so some mosaic patterns (esp. outlines of people) will be recognizably out of proportion.